Display omitted •The doping of Cu added and enhanced the generating routes of ROSs.•The proposed HEEF system exhibited high efficiency, stability and economy.•Free risk of secondary pollution of heavy metal (Cu) was proved.•Reasonable mechanism was proposed.•Degradation pathways were speculated with several typical intermediates identified. The degradation of tetracycline (TC) in aqueous environment has been studied by a novel heterogeneous electro-Fenton (HEEF) process using Cu-doped Fe@Fe2O3 core–shell nanoparticles (CFF) as catalyst loaded on the nickel foam as cathode. CFF was synthesized by a facile two-step reduction method and aging process, and characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), scanning transmission electron microscopy mapping (STEM-mapping), X-ray diffractometer (XRD) and X-ray photoelectron spectroscopy (XPS). The effects of operating parameters, such as the initial pH of solution, the mass ratio of Cu/Fe and aeration mode, were investigated. The prepared CFF exhibited rapid degradation (98.1% within 2 h) and high mineralization efficiency of TC (89.8% after 6 h). Furthermore, the degradation of TC in solution remained over 90% till the seventh cycle, indicating the high stability of CFF. The mechanism of the HEEF process catalyzed by CFF was also proposed. Additionally, based on the identification of main representative by-products, plausible pathways for the mineralization of TC in aqueous solution by OH was speculated.